Permanent magnet electrical machine rotors, such as the rotors for permanent magnet electrical machines and, more particularly, high speed and/or power electrical machines, may be designed to mechanically restrain the magnets against the centrifugal forces present during operation of the electrical machine and/or to manage thermal stresses. Examples of permanent magnet electrical machine rotors are disclosed in U.S. Pat. Nos. 5,111,094 and 6,047,461; in UK Patent Application Publication No. GB2299217A; and in Japan Published Unexamined Patent Application No. JP10-225032A. The disclosures of these and all other publications referenced herein are incorporated by reference in their entirety for all purposes.